A double tee beam is a load-bearing structure that resembles two T-beams connected to each other side by side. The strong bond of the flange (horizontal component) and the two vertical components (also known as stems) creates a structure that is capable of withstanding high loads while having a long span. Floor systems of modern parking structures, for example, use precast double tee beams, which are joined flange-to-flange using connectors anchored in the flange of the double tee beams, to form an integral multi-beam floor.
A type of conventional flange-to-flange connector uses a thin twisted plate pre-embedded in the flange. Two twisted plates aligned with each other across the gap between double tees are welded together at the jobsite using a loose steel plate to connect the flanges. This type of flange-to-flange connector creates a flexible connection, which has been criticized for lack of fatigue capacity and failure of welds if the welding is not done properly by certified welders. In addition, this type of flange-to-flange connector requires caulking (sealant) to seal the gap between the flange edges, with a life expectancy of five to ten years, thus requiring significant maintenance expenses.